Effect of Heat Treatment Procedures on Microstructure and Mechanical Properties of Nodular Iron

Abstract

In their bid to produce cast iron latter than Malleable Iron, the scientist discovered the ductile iron or S.G. Iron (spherodial Graphite iron) way back in 1948.The use of this type of cast iron as an engineering material has been increasing day by day ever since its discovery. It is now replacing steel in many important engineering applications. The production of S.G Iron increased to a large extent during last two decades.
The excellent combination of mechanical properties obtained in S.G. iron can further be informed by the heat treatment. The most recent development in this regard is the production of Austempered Ductile Iron (ADI).It provides an excellent combination of high tensile strength, wear resistance along with good corrosion resistance and quite significant amount of ductility.
Due to these factors, S.G. or ductile iron are austempered when a very favourable combination of various properties is required. But this type of treatment is bit tricky,since it require controlled heating and isothermal holding of the material. So it is necessary to find some attractive methods for property development in S.G. iron.
In the present work conventional heat treatment proceeds like annealing, normalizing and tempering of the material has been performed. The mechanical properties obtain by various technique have been compared to one another.In this work two different grades of S.G. Iron (one with copper and another without copper) have been used. The effect of the alloying element (i.e. copper) has also been studied.